PROJECT SUMMARY/ABSTRACT Diarrhea is the second leading cause of death for children around the world. This is true despite the fact that nearly all such deaths could be prevented with a simple and inexpensive solution: oral rehydration salts (ORS). Private health care providers, who treat the majority of childhood illness in low- and middle-income countries (LMICs), are particularly unlikely to dispense ORS to children with diarrhea. Instead, providers often dispense antibiotics inappropriately. Recognizing this significant challenge, several international organizations (including USAID) have invested heavily in trying to increase ORS dispensing in the private sector. In the absence of evidence on why ORS is so inconsistently dispensed by private providers, however, several interventions to promote private sector ORS dispensing have been ineffective. Clearly, a critical and urgent next step is to examine the key drivers of underprescription of ORS and overprescription of antibiotics in the private sector in order to inform efforts to improve diarrhea care. In this study, we examine several leading explanations for poor quality of care for child diarrhea in the private sector. First, patient preferences for ORS alternatives (e.g., an antibiotic) could be driving underprescription of ORS. We will identify the causal effect of patient preferences (Aim 1) by having anonymous standardized patients (SPs) pose as caretakers of children with diarrhea and express different (randomly assigned) preferences for treatment (ask for ORS, ask for antibiotics, or let provider decide). Second, private providers could be responding to financial incentives to sell more profitable alternatives to ORS (e.g., an antibiotic). To estimate the causal effect of financial incentives (Aim 2), we will instruct a subset of SPs to inform providers that they can get discounted treatments at a relative?s drug shop. This eliminates the provider?s financial incentive to recommend a given treatment and allows us to estimate the effect of such incentives. Finally, private providers might not directly distribute ORS or could have frequent stock-outs. To estimate the causal effect of stock-outs (Aim 3), we will randomly assign half of the providers to receive a three-month supply of ORS. This generates exogenous variation in stock outs and thus enables us to isolate the causal effect of stock outs on ORS and antibiotic prescribing. Combining, (a) causal estimates of the impact of each factor on prescribing, and (b) population estimates of the prevalence of each factor, will allow us to estimate the population level impact of implementing interventions that address each factor (Aim 4). This study will provide the most comprehensive evidence to date on why one of the most important health technologies in history is often not prescribed. The results will inform the design of interventions aimed at increasing ORS dispensing and reducing antibiotic dispensing. If such interventions are targeted appropriately, millions of young lives could be saved.